I was thinking of making two of these, but looking at the component overlay, I see that each Varislope phaser uses 6 of the DG419 electronic switches. I can't seem to find these from any of my regular suppliers, and others that I have found are charging £3-£6 each IC. Is that a normal price? That adds considerably to the cost of this board (I found the TDA1022's much cheaper ) and it is sort of putting me off, does anyone know of anywhere in the UK (or accessible to an Englishman!) who sells these chips for a reasonable price?

Or maybe they're just pricey and I need to get over myself

Thanks,

Charlie

(Don't get me wrong I'm not being a tightwad, just watching the pennies!)

I was thinking of making two of these, but looking at the component overlay, I see that each Varislope phaser uses 6 of the DG419 electronic switches. I can't seem to find these from any of my regular suppliers, and others that I have found are charging £3-£6 each IC. Is that a normal price? That adds considerably to the cost of this board (I found the TDA1022's much cheaper ) and it is sort of putting me off, does anyone know of anywhere in the UK (or accessible to an Englishman!) who sells these chips for a reasonable price?

Or maybe they're just pricey and I need to get over myself

Thanks,

Charlie

(Don't get me wrong I'm not being a tightwad, just watching the pennies!)

These are just electronic switches. If you only want *either* a phaser *or* a Low Pass Filter, you can completely omit them and replace them with a piece of wire.

And even with the LPF / Phaser option, you can use normal, mechanical switches instead of the DG419. I did this myself, in the JH-3 module that was the first prototype of the Varislope Phaser/Filter. But in that case, you must keep the wires to the switches short ( a few centimeter), and keep them at a distance from other components and wires. (Use stiff wires that keep their shape for this.)

Also, I don't know if I've mentioned it before:
All LM13600s can be replaced with LM13700s.

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

I hadn't thought of that (being possible) I must say I'm all for more toggles and knobs etc!

So going by what you suggest, I'd simply connect an SPDT switch, with the common soldered to the pad for pin 1 of the DG419, and the two poles soldered to the pads for pins 2 and 8. Leaving all other pad connections untouched I guess.

Though looking at the schematic I'm a little confused by how the APF/LPF jumper is used, it seems to suggest attaching lots of SPST's to that, which will control the DG419 (sw1, sw2 etc)

Sorry for the confusion, it may be apparent at this point that I'm a dullard (noob) when it comes to going off piste!

So going by what you suggest, I'd simply connect an SPDT switch, with the common soldered to the pad for pin 1 of the DG419, and the two poles soldered to the pads for pins 2 and 8. Leaving all other pad connections untouched I guess.

Exactly.

Quote:

Though looking at the schematic I'm a little confused by how the APF/LPF jumper is used, it seems to suggest attaching lots of SPST's to that, which will control the DG419 (sw1, sw2 etc)

Each DG419 has its own 100k pullup resistor to positive supply. So leaving the pin open means LPF, and connecting it to GND means APF.

You can use 6 individual switches if you like, or (as I did) switch the DG's in pairs, shorting two adjacent pins that control the DG's together, and only use 3 switches.

(If you don't use the DG's, and want to switch directly, you need three 2p2t switches of course, or six 1p2t.)

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

30V capability. (No need for a bunch of extra circuitry to put a 4066 on +/-7.5V supplies and clamping the signals at sensitive points where any parasitic capacitance interferes with the not-so-big 150pF nominal integration capacitance ...

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

(2) Omit all DG419 chips and connect Pin1 to Pin2 on each DG419 footprint.

Not tested by me, but it should work!

(Please report back if you have tried it. )

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

I've got the PCB mostly built as I'm just waiting for a few back-ordered parts.

I've found a couple of errors in the BOM.
There should be no 430K resistors in the BOM. The quantity listed is blank.
There should be nineteen 15K resistors, not twenty.
There should be three 51K resistors, not two.

I also had a couple of connector part number errors so if anyone downloaded a copy of my Mouser BOM you should get the current file on my site. There's also a picture of the mostly assembled PCB along with my proposed modifications.

DaveLast edited by davebr on Tue Jul 07, 2009 9:42 am; edited 1 time in total

I finished building my Variable slope filter/phaser some days ago and calibrated it yesterday. I managed to put one 13600 in the wrong way when I first fired it up and the chip obviously got damaged. After replacing the damaged 13600 with a new one, the module started working for the most part.
While the modulation section and phasing works/sounds fine with self-oscillation starting at about 12 o'clock on the feedback pot, the output level is considerably lower on filter mode and self-oscillation only works when cutoff pot is set around 9o'clock to 12o'clock.
The self-osc in LPF mode also fades to silence at certain frequency, so it only works at low frequencies (rough estimate would be up to about 800hz). I maxed out the feedback trimmer to get these results. If the feedback trimmer is set lower, then I can't get self-osc at any setting of cutoff pot.

I have already triple-checked the wiring, orientation of chips and transistors, tested that all switches are working properly and calibrated the unit once again, but it seems I can't find the reason to the volume drop when the unit is in LPF mode, but I did notice that the volume drop occurs when switch contacts 3 and 4 (of the afp/lpf connector) are not grounded. The position of other switches don't affect the volume drop at all.

I finished building my Variable slope filter/phaser some days ago and calibrated it yesterday. I managed to put one 13600 in the wrong way when I first fired it up and the chip obviously got damaged. After replacing the damaged 13600 with a new one, the module started working for the most part.
While the modulation section and phasing works/sounds fine with self-oscillation starting at about 12 o'clock on the feedback pot, the output level is considerably lower on filter mode and self-oscillation only works when cutoff pot is set around 9o'clock to 12o'clock.
The self-osc in LPF mode also fades to silence at certain frequency, so it only works at low frequencies (rough estimate would be up to about 800hz). I maxed out the feedback trimmer to get these results. If the feedback trimmer is set lower, then I can't get self-osc at any setting of cutoff pot.

I have already triple-checked the wiring, orientation of chips and transistors, tested that all switches are working properly and calibrated the unit once again, but it seems I can't find the reason to the volume drop when the unit is in LPF mode, but I did notice that the volume drop occurs when switch contacts 3 and 4 (of the afp/lpf connector) are not grounded. The position of other switches don't affect the volume drop at all.

Any help would be much appreciated.

Then you probably have something wrong in stage 3 or 4 of the 6 filter stages. I would focus debugging on these stages, and compare it with other stages.

BTW, "Slope" also has an influence at the self oscillation point. Best to test it all with Slope fully ccw. (Steepest slope.)

JH._________________"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)

Well, I have finished to mount one. Let's say, it is still at a prototype level...
I set different setting to be able to ear the result for exemple in self oscillation and with the LFO modulation.
Today, I connect it to the kobol to get more experiments.

Then you probably have something wrong in stage 3 or 4 of the 6 filter stages. I would focus debugging on these stages, and compare it with other stages.

BTW, "Slope" also has an influence at the self oscillation point. Best to test it all with Slope fully ccw. (Steepest slope.)

JH.

Hi again,

After solid debugging from morning to night yesterday I continued the debugging in the morning today. I took out every dg419 and put a jumper from pin 1 to 8 to confirm once again that the switches are not causing any funkiness. All ok. then I triple checked every solder joint and component in stages 3-4, all ok. Also the voltages seemed to be almost exactly the same between the corresponding points between different stages. At this point, I calibrated my scope and traced the audio from the input to stage 4 and noticed the signal became weaker in stage 4. Ok, that's it, I replaced U7 and now I have resonance like never before. Also the audio level in LPF mode rose somewhat, although it's still tad lower than on APF mode... I guess it's normal?

Anyway, I couldn't believe I had a bad 13600 straight out of the box and that caused me quite a bit of headache. The bad part was a JRC one.

Oh yes, this is a very nice addition to my modular and actually the first JH project I put in my modular and not in a separate case. I'll post a pic to the picture thread if you don't mind to see some dymo-tape madness?

It has a 1K output resistor - I notice for your mod you have no output resistor - the output of the TL074 goes straight into the IN pad of the PCB - would I want to exclude the 1K resistor here and use a jumper instead?

Also, are those 100K Audio taper pots for the input attenuators?

And for the output buffer, I'm assuming I could use a TL072 here fine and that you used a TL074 for the extra op-amps for the other mods you did, right?

Thanks!

davebr wrote:

I powered up my board tonight and gave it a preliminary checkout.

I finalized my panel layout and included a design for the Wave knob that included both waveform legends and tic marks. The .fpd file is on my website.

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